)(y-2)3.4.x(x-2)-(x+5)(x-5)5.6.7.8.9.(x-3y)(x+3y)-(x-3y)210.11.12.13.0.125100×810014.15.(16—19题用乘法公式计算16.999×100117.18.19.20.化简求值:,其中。21.化简求值,其中。22.5(x-1)(x+3)-2(x-5)(x-2)23.(a-b)(a2+ab+b2)24.(3y+2)(y-4)-3(y-2)(y-3)25.a(b-c)+b(c-a)+c(a-b)26.(-2mn2)2-4mn3(mn+1)27.3xy(-2x)3·(-y2)228.(-x-2)(x+2)29.5×108·(3×102)30.(x-3y)(x+3y)-(x-3y)231.(a+b-c)(a-b-c)答案1.a-2b2.5x+y+8?3.4x2+y24.-2x+255.x2-4y26.16y4-81x47.4a2+28.x+39.6xy-18y210.-x2+4x-411.24xy12.x4-2x2y2+y413.114.1015.161216.原式=(1000-1)×(1000+1)17.原式=(99+1)×(99-1)=1000000-1=100×98=999999=980018.原式=(900-2)219.原式=20092-(2009+1)(2009-1)=10000-400+4=20092-20092+1=9604=120.原式=6a2+3a-3,当a=2时,原式=6×-22+3×-2-3=1521.原式=-x2+6xy,当x=2,y=12时,原式=--22+6×-2×12=-1022.-3x2+24x-3523.a3-b324.5y-2625.026.-4mn327.-32x4y528.-x2-4x-429.1.5×101130.6xy-18y231.a2-2ac+c2-b2
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